Effects Of Post-Anthesis Waterlogging On Grain Yield And Quality Formation In Different Quality Wheat Cultivars And Its Physiological Mechanism

Soil waterlogging is major natural adversity in wheat production in China, and waterlogging during mid to late growth stage is a major factor of limiting grain yield and quality formation. Elucidating the physiological mechanism and regulation principles for grain yield and quality formation in wheat is of important significance for understanding grain yield and quality physiology and guiding cultural management in wheat under post-antheais waterlogging. The effects of waterlogging on grain yield and quality of two wheat varieties (Triticum aestivum L) differring in grain protein content including Yangmai 9 with low protein content and Yumai 34 with high protein content were studied in a pot culture experiment. Two water treatments were established from anthesis to maturity, i.e. soil relative water content maintaining at 70-80% as control, and maintaining 1-2 cm water layer above the soil as waterlogging treatment. The effects of post-anthesis waterlogging on photosynthesis and senescense of flag leaf, carbon and nitrogen metabolize, root characteristics and senescence, grain yield and quality formation in different wheat varieties. Here are the main results.1. Effects of post-anthesis waterlogging on photosynthesis, senescense of flag leaf and matter redistribution in wheatWaterlogging significantly reduced chlorophyll content, stomatal conductance, transpitation rates and photosynthetic rate, and Yumai 34 decreased much faster than Yangmai 9. Ratios of variable to maximum and variable to initial fluorescence, actual photosynthetic efficiency, and photochemical quenching were much lower, while initial fluorescence and non-photochemical quenching were much higher under waterlogging than in control, indicating damage to photosystemâ…¡. Waterlogging decreased activities of superoxide dismutase and catalase in both cultivars, and activity of peroxidase (POD) in Yumai 34, while POD activity in Yangmai 9 was mostly increased. The obvious decrease in the amount of post-anthesis accumulated dry matter and kernel filling rate which was redistributed to grains, also contributed to the grain dry matter loss under Waterlogging.2. Effects of post-anthesis waterlogging on nitrogen assimilation and translocation in wheatWaterlogging reduced nitrogen content and accumulation of leaf, grain, plant, stem and sheath. Compared with CK, waterlogging increased distribution of nitrogen in vegetative organs, while reduced distribution of nitrogen in grain. Nitrogen translocation amount of pre-anthesis assimilate in Yangmai 9, nitrogen translocation rate of pre-anthesis assimilate in Yumai 34 and nitrogen post-anthesis assimilates accumulation in two wheat were significantly reduced under post-anthesis waterlogging.3. Effects of post-anthesis waterlogging on wheat root characteristics and senescencePost-anthesis waterlogging significantly reduced root weight and root activity. Compared with CK, waterlogging reduced the activities of protective enzymes as superoxide dismutase (SOD) and catalase (CAT) in root, while increased the content of malondiadhyde (MDA) and the activity of peroxidase (POD), thus enhanced root membrane lipid peroxidation. In addition, significant relativities between root activity, root weight, catalase (CAT), the content of malondiadhyde (MDA) and index of carbon and nitrogen metabolize, grain quality were observed.4. Effects of post-waterlogging on grain yield and quality in wheatWaterlogging significantly reduced grain 1000-kernel weight, grain yield, protein content, ratios of amylopectin to amylose content and glutelin to gliadin content, while increased amylose and protein content. Compared with CK, waterlogging increased grain flour wet and dry gluten, reduced gluten index, sedimentation volume and falling number.In conclusion, enhanced root and flag leaf senescence, decreased in nitrogen assimilate translocation and dry matter accumulation translocation were involved in the depressed grain yield, protein and starch content in wheat under waterlogging. Further studies revealed that depressed anti-oxidative enzyme activities, root activity and flag leaf photosynthetic characteristics were key physiological mechanisms in affecting the grain yield and quality formation under post-anthesis waterlogging.